Mitigating an induced electrical signal from an appliance in a powered-off state

ABSTRACT

An isolation unit may include input pins to receive an electrical signal induced by ambient sound waves incident on an appliance in a powered-off state, one or more first transformers, connected to the input pins, to electrically isolate the induced electrical, one or more second transformers, connected to the first transformers, to provide a common mode choke function on the induced electrical signal, one or more inductors, connected to the one or more second transformers, one or more resistors, connected to the one or more inductors, wherein the one or more inductors and the one or more resistors are configured to limit an amplitude of a current of the induced electrical signal, and output pins, connected to the one or more inductors, to receive a modified electrical signal from the one or more inductors to propagate the modified electrical signal to a downstream cable.

RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/333,091 entitled “Mitigating An Induced ElectricalSignal From An Appliance In A Powered-Off State” filed May 6, 2016, theentire contents of which is hereby incorporated by reference.

BACKGROUND

Communication security is a vital part of many aspects of government andbusiness. While encryption and other means of signal obfuscation mayprovide a layer of security for communication devices when such devicesare in operation, consideration must also be given to signal securityeven when such devices are not in operation, such as in a powered downor inoperative state.

SUMMARY

The various embodiments include systems and methods of mitigating aninduced electrical signal from an appliance. In some embodiments, theinduced electrical signal may be induced by ambient sound waves incidenton an appliance. In some embodiments, the induced electrical signal maybe induced by ambient sound waves incident on the appliance when theappliance is in a powered-off state. In various embodiments, the inducedelectrical signal may be a triboelectrically or piezoelectricallyinduced electrical signal from the appliance when the appliance is in apowered-off state.

In various embodiments, the isolation unit may operate on the inducedelectrical signal to produce a modified signal, such that the modifiedsignal output by the isolation unit, e.g., when propagated from theisolation unit through a downstream cable, cannot be transformed toextract an intelligible audio signal. Thus, the modified signal, whentransformed to extract an audio signal, may only provide anunintelligible audio signal. In some embodiments, the unintelligibleaudio signal may be an unintelligible speech signal.

Various embodiments may include an isolation unit, which may includeinput pins, configured to receive an induced electrical signal that isinduced by ambient sound waves incident on an appliance when theappliance is in a powered-off state, one or more first transformers,connected to the input pins, configured to electrically isolate theinduced electrical signal, one or more second transformers, connected tothe one or more first transformers, configured to receive the inducedelectrical signal from the one or more first transformers, and furtherconfigured to provide a common mode choke function on the inducedelectrical signal, one or more inductors, connected to the one or moresecond transformers, and one or more resistors, connected to the one ormore inductors, wherein the one or more inductors and the one or moreresistors are configured to limit an amplitude of a current of theinduced electrical signal, and output pins, connected to the one or moreinductors, configured to receive a modified electrical signal from theone or more inductors, and configured to propagate the modifiedelectrical signal to a downstream cable.

In some embodiments, the one or more first transformers may be furtherconfigured to provide a frequency filtration function on one or morefrequencies of the induced electrical signal. In some embodiments, theone or more second transformers may be further configured to cancel oneor more aspects of an amplitude of the induced electrical signal. Insome embodiments, the modified electrical signal may not be transformedinto an intelligible audio signal

In various embodiments, the isolation unit may include a signalmodifier. In some embodiments, the signal modifier may be configured toreceive an induced electrical signal from an appliance, wherein theinduced electrical signal is induced by ambient sound waves incident onthe appliance, modify the induced electrical signal to produce amodified electrical signal that may not be transformed into anintelligible audio signal, and output the modified electrical signal. Insome embodiments, the induced electrical signal may be one oftriboelectrically induced by ambient sound waves incident on theappliance and piezoelectrically induced by ambient sound waves incidenton the appliance. In some embodiments, the induced electrical signal maybe induced by the ambient sound waves incident on the appliance when theappliance is in a powered-off state.

In some embodiments, the signal modifier may further include one or morefirst transformers, configured to electrically isolate the inducedelectrical signal. In such embodiments, the one or more firsttransformers may be configured to provide a frequency filtrationfunction on one or more frequencies of the induced electrical signal. Insome embodiments, the one or more first transformers may be configuredto attenuate the one or more frequencies of the induced electricalsignal in range of from approximately 200 Hz to approximately 10,000 Hz.In some embodiments, the one or more first transformers may beconfigured to attenuate the one or more frequencies of the inducedelectrical signal in a range of from approximately 300 Hz toapproximately 5,000 Hz. In some embodiments, the signal modifier may befurther configured such that an amplitude of the modified electricalsignal is substantially below −120 dB.

In some embodiments, the signal modifier may further include one or moresecond transformers, configured to receive the induced electrical signalfrom the one or more first transformers, and further configured toprovide a common mode choke function on the induced electrical signal.In some embodiments, the one or more second transformers may beconfigured to cancel one or more aspects of an amplitude of the inducedelectrical signal.

In some embodiments, the signal modifier may further include one or moreinductors, configured to limit an amplitude of a current of the inducedelectrical signal. In some embodiments, the signal modifier may furtherinclude one or more resistors, in communication with the one or moreinductors, wherein the one or more inductors and the one or moreresistors are configured to limit the amplitude of the current of theinduced electrical signal.

Further embodiments may include a method of modifying an inducedelectrical signal is induced by ambient sound waves incident on anappliance. Further embodiments may include an isolation unit includingmeans for performing functions of the methods described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments, andtogether with the general description given above and the detaileddescription given below, serve to explain the features of variousembodiments.

FIG. 1 is a block diagram of a conventional communication system.

FIG. 2 is a block diagram of a communication system according to variousembodiments.

FIG. 3 is a block diagram of a communication system according to variousembodiments.

FIG. 4 is a component diagram illustrating an embodiment isolation unit.

FIG. 5 is a circuit diagram illustrating a power injection unit of anembodiment isolation unit.

FIG. 6 is a circuit diagram illustrating a signal modifier of anembodiment isolation unit.

FIG. 7 is a circuit diagram illustrating a signal modifier subunit of anembodiment isolation unit.

FIG. 8 is a process flow diagram illustrating a method for mitigating aninduced electrical signal from an appliance in a powered-off stateaccording to various embodiments.

FIGS. 9A-H are plots illustrating test results of an embodimentisolation unit.

DETAILED DESCRIPTION

Various embodiments will be described in detail with reference to theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.References made to particular examples and implementations are forillustrative purposes, and are not intended to limit the scope ofvarious embodiments or the claims.

Communication security is a vital part of many aspects of government andbusiness. While encryption and other means of signal obfuscation mayprovide a layer of communication security for communication devices whensuch devices are in operation, consideration must also be given to thesecurity of signals that may be generated even when such devices are notin operation, such as in a powered down or inoperative state (e.g., whena telephone is in an on-hook state, or when a printer is idle and notoperating to form images).

The various embodiments include systems and methods of mitigating aninduced electrical signal from an appliance in a powered-off orpowered-down state. In various embodiments, an isolation unit may becoupled to an appliance to mitigate a triboelectrically- or apiezoelectrically-induced signal emanating from the appliance. In someembodiments, the electrical appliance may be in a powered-off state, andthe electrical signal emanating from the appliance may be induced byambient sound encountering a surface of the appliance that may vibrate.The vibrating surface may include one or more portions of a body of theappliance (such as an exterior surface, a shell, a casing, or a housing)or another component of the appliance, for example, a window, a panel, abutton, a switch, a cover, or another element of the appliance that mayencounter incident sound waves. In some embodiments, the electricalsignal emanating from the appliance may be induced by sound waves ofambient speech that encounter a surface of the appliance. The inducedelectrical signal may propagate along a propagation path coupled to theappliance, such as a cable coupled to the appliance. Further, theinduced electrical signal may be detected along a path of propagation(e.g., the cable) and the detected electrical signal may be transformedto extract intelligible audio, including intelligible speech. Thus, theinduced triboelectrical signal or a piezoelectrical signal emanatingfrom the appliance may represent a security vulnerability for suchlocations where such appliances are used.

In various embodiments, the isolation unit may receive the electricalsignal from the appliance (e.g., the triboelectrically- or apiezoelectrically-induced signal emanating from the appliance in apowered-off state) and may operate on the electrical signal to produce amodified signal, such that the modified signal, when propagated througha propagation path, cannot be transformed to extract an intelligibleaudio signal. In some embodiments, the modified signal, when propagatedthrough a propagation path, cannot be transformed to extract anintelligible speech signal.

In various embodiments, the isolation unit may receive an electricalsignal from the appliance (e.g., the triboelectrically- or apiezoelectrically-induced signal emanating from the appliance in apowered-off state) and may operate on the electrical signal to produce amodified signal having a signal level that is below a threshold signallevel. In some embodiments, the threshold signal level may be determinedsuch that the modified signal cannot be transformed to extract anintelligible audio signal. In various embodiments, the modified signalmay be below the threshold signal level such that the isolation unitsatisfies one or more security requirements and/or regulations. Forexample, the isolation unit may operate on the electrical signal toproduce a modified signal such that the isolation unit may satisfy theCommittee on National Security Systems (CNSS) Instruction No. 5001. Insome embodiments, the isolation unit may enable an appliance coupled tothe isolation unit to satisfy the one or more security requirementsand/or regulations (e.g., CNSS Instruction No. 5001).

FIG. 1 illustrates a conventional communication system 100. An appliance104 may communicate with a communications network 106 via acommunication link 108. A portion of communication link may include aphysical connector 110 to couple the appliance 104 to, for example, acommunications jack, a modem, router, or another network communicationdevice or connection outlet. The appliance 104 may also be coupled to apower supply, such as electrical outlet 114, via electrical cable 116.The appliance 104 may include any device that may communicate with thecommunications network 106 over the communication link 108, such as avoice over Internet protocol (VoIP) telephone, a computer, a printer, anetwork connected storage device, a router, a modem, or another similardevice.

When the appliance 104 in a powered-off state (e.g., is not inoperation), the appliance 104 may yet emanate small electrical signals.For example, ambient sound waves in the location of the appliance 104may encounter a surface of the appliance 104. The appliance 104 mayemanate an electrical signal that is triboelectrically orpiezoelectrically induced based on the ambient sound waves. The inducedelectrical signal may propagate along the physical connector 110.Further, the induced electrical signal 112 may be detected by a detector120, such as a signal detector directly or indirectly coupled to thephysical connector 110 (e.g., by a wired or wireless connection).

The electrical signal that is detected by the detector 120 may betransformed into an audio signal. In some cases, the detected electricalsignal may be transformed into an intelligible audio signal such thatthe induced electrical signal may be used to eavesdrop on audio (e.g.,conversations) in proximity to the appliance 104.

FIG. 2 illustrates a communication system 100 suitable for use with thevarious embodiments. With reference to FIGS. 1 and 2, the appliance 104may be coupled to an isolation unit 102 by a connector 124. Theisolation unit may be coupled to the physical connector 110 of thecommunication link 108 such that communications from the appliance 104to the communication network 106 pass through the isolation unit 102.The isolation unit 102 may also be coupled to a power supply, such asthe electrical outlet, via the electrical cable 116. In variousembodiments, the isolation unit 102 may modify 122 triboelectrically orpiezoelectrically induced electrical signals emanated by the appliance104, such as triboelectrically or piezoelectrically induced electricalsignals emanated by the appliance 104 in a powered-off state. In someembodiments, the isolation unit 102 may operate on the electrical signalto generate a modified electrical signal. The modified electrical signalmay then propagate from the isolation unit 102 via the physicalconnector 110. In various embodiments, the isolation unit 102 may modifythe electrical signal such that even if the modified electrical signalis detected by the detector 120, the modified electrical signal ismitigated such that the modified electrical signal may not betransformed into an intelligible audio signal. In some embodiments, theisolation unit 102 may operate on the emanated electrical signal suchthat the mitigated electrical signal is below a threshold amplitude.

FIG. 3 illustrates a communication system 300 suitable for use with thevarious embodiments. With reference to FIGS. 1-3, the isolation unit 102may include a signal modifier 302, a power injection unit 304, and apower input 306. The power input 306 may receive power, for example,from an electrical source such as a direct current (DC) source or analternating current (AC) source, such as an electrical outlet. The powerinput 306 may provide the received power to the power injection unit304. The power injection unit 304 may provide power to the appliance104, e.g., via a connection 308 a. The power injection unit 304 may alsobe coupled to the signal modifier 302. In some embodiments, the powerinjection unit may provide the power to the appliance 104 via aconnection 308 b between the signal modifier 302 and the appliance 104.In some embodiments, the connections 308 a and 308 b may be a singleconnector (e.g., a single physical cable) between the isolation unit 102and the appliance 104.

The signal modifier 302 may be coupled to the appliance 104 such thatthe signal modifier 302 may receive a triboelectrically orpiezoelectrically induced electrical signal from the appliance 104, suchas triboelectrically or piezoelectrically induced electrical signalsemanated by the appliance 104 in a powered-off state. The signalmodifier 302 may operate on the induced electrical signal to produce amodified signal. The signal modifier 302 may pass the modified signal tothe physical connector 110.

FIG. 4 is a component diagram illustrating an embodiment isolation unit400. With reference to FIGS. 1-4, the isolation unit 400 may be similarto the isolation unit 102. The isolation unit 400 may include a housingcomprising a first housing component 402 and a second housing component404, which may be coupled to enclose other components of the isolationunit 400, for example, via screws inserted through screw holes 416.

The isolation unit 400 may also include a circuit board 406. The circuitboard 406 may include an appliance connector 408 and a networkcommunications connector 410. The appliance connector 408 may enable theisolation unit 400 to be coupled to an appliance (e.g., the appliance104). The network communications connector 410 may enable the isolationunit 400 to be coupled to a physical connector (e.g., the physicalconnector 110) to enable network communications.

The isolation unit 400 may also include a power connector 412, which mayenable the isolation unit 400 to be coupled to a power supply. Suppliedpower may be provided to the circuit board 406 from the power connector412 via a power cable 414. In some embodiments the power connector 412may include an AC/DC converter.

FIG. 5 is a circuit diagram illustrating a power injection unit 500 ofan embodiment isolation unit. With reference to FIGS. 1-5, the powerinjection unit 500 may be similar to the power injection unit 304 of theisolation unit 102. The power injection unit 500 may include a powerinput 502 (which may be similar to the power connector 412 and the powerinput 306) which may enable the power injection unit 500 to receiveelectrical power (e.g., from a DC power source). The power injectionunit 500 may also include a power coupling 504, which may be configuredto provide electrical power to the isolation unit 102. In someembodiments, the power injection unit 500 may be configured to provideelectrical power to an appliance (e.g., the appliance 104) together witha communications connection, such as by Power Over Ethernet (POE). Thepower injection unit 500 may also include various other electroniccomponents, including resistors, capacitors, ground connections,description of which is omitted for brevity.

FIG. 6 is a circuit diagram illustrating a signal modifier 600 of anembodiment isolation unit. With reference to FIGS. 1-6, the signalmodifier 600 may be similar to the signal modifier 302. The signalmodifier 600 may include an appliance connector 602 (which may besimilar to the appliance connector 408) to that may enable the signalmodifier 600 to be coupled to an appliance (e.g., the appliance 104). Insome embodiments, the appliance connector 602 may receive atriboelectrically or piezoelectrically induced electrical signal fromthe appliance 104.

The signal modifier 600 may also include a power coupling 604, which maybe coupled to the power coupling 504 of the power injection unit 304.The power coupling 604 may be configured to receive power from the powercoupling 504 such as that power may be provided to an appliance that iscoupled to the isolation unit.

The appliance connector 602 and the power coupling 604 may each becoupled to a signal modifier subunit 700. The signal modifier subunit700 may be configured to receive the induced electrical signal from theappliance connector 602, modify the induced electrical signal, and topass the modified electrical signal to one or more output pins 712 (FIG.7).

FIG. 7 is a circuit diagram illustrating a signal modifier subunit 700of an embodiment isolation unit. With reference to FIGS. 1-7, the signalmodifier subunit 700 may include input pins 702, one or more firsttransformers 704, one or more second transformers 706, one or moreinductors 708, one or more resistors 710, and one or more output pins712. The signal modifier subunit 700 may receive an induced signal 750at one or more of the input pins 702, such as triboelectrically orpiezoelectrically induced electrical signal from an appliance (e.g., theappliance 104) in a powered-off state.

The induced electrical signal may then be passed to the firsttransformers 704. The first transformers 704 may include inductor coilsto electrically isolate the induced electrical signal. In someembodiments, the first transformers 704 do not include metallicconnections such the first transformers 704 do not provide any metallicelectrical connection. Thus, the first transformers 704 provide atransformer-only coupling for the electrical signal. In someembodiments, the first transformers 704 may operate to provide afrequency filtration function on one or more frequencies of the inducedsignal. In some embodiments, the first transformers 704 may attenuateone or more frequencies of the electrical signal in a range ofapproximately 200 Hz-10,000 Hz. In some embodiments, the firsttransformers 704 may attenuate one or more frequencies of the electricalsignal in a human voice speech range (e.g., approximately 300 Hz-5,000Hz).

The electrical signal may then pass to second transformers 706. In someembodiments, the second transformers 706 may provide a common mode chokefunction. In some embodiments, the second transformers 706 may operateto electromagnetically cancel one or more aspects of an amplitude of theelectrical signal.

The electrical signal may then pass to the inductors 708, and then tothe resistors 710. The inductors 708 and/or the resistors 710, alone orin combination, may operate to provide impedance matching to theelectrical signal. The inductors 708 and the resistors 710, alone or incombination, may also operate to limit an amplitude of a current of theelectrical signal. In some embodiments, the inductors 708 and/or theresistors 710 may modify the electrical signal to reduce an amplitude ofthe electrical signal to be substantially below −120 dB. In someembodiments, the inductors 708 and/or the resistors 710 may modify theelectrical signal to reduce an amplitude of the electrical signal suchthat an amplitude component of the electrical signal (e.g., a portion ofthe overall amplitude of the electrical signal) may be above −120 dB,and no intelligible audio signal (or intelligible voice signal) may berecovered from the electrical signal.

The signal modifier subunit 700 may then provide a modified signal 754via the output pins 712. In some embodiments, the output pins 712 may bea component of a connector, such as an RJ-45 cable connector, to enablea connection of the isolation unit to a physical connector, such as thephysical connector 110.

The modified signal may propagate through a downstream cable (e.g., thephysical connector 110). In various embodiments, the modified signalcannot be transformed to extract an intelligible audio signal. In someembodiments, the unintelligible audio signal may be an unintelligiblespeech signal.

FIG. 8 is a process flow diagram illustrating a method 800 formitigating an induced electrical signal from an appliance in apowered-off state. With reference to FIGS. 1-8, the method 800 may beimplemented by an isolation unit (e.g., the isolation unit 102, 400).

In block 802, the isolation unit may receive an induced electricalsignal. For example, the isolation unit may receive may an inducedelectrical signal, such as a triboelectrically or piezoelectricallyinduced electrical signal from an appliance (e.g., the appliance 104) ina powered-off state.

In block 804, the isolation unit may transform the electrical signalusing one or more first transformers. For example, the isolation unitmay pass the induced electrical signal to the first transformers 704.The first transformers 704 may include inductor coils to electricallyisolate the induced electrical signal. In some embodiments, the firsttransformers 704 do not include metallic connections such the firsttransformers 704 do not provide any metallic electrical connection.Thus, the first transformer 704 provide a transformer-only coupling forthe electrical signal. In some embodiments, the first transformer 704may operate to provide a frequency filtration function on one or morefrequencies of the induced signal.

In block 806, the isolation unit may transform the electrical signalusing one or more second transformer. For example, the isolation unitmay pass the electrical signal from the first transformers 704 thesecond transformers 706. In some embodiments, the second transformers706 may provide a common mode choke function. In some embodiments, thesecond transformers 706 may operate to electromagnetically cancel one ormore aspects of an amplitude of the electrical signal.

In block 808, the isolation unit may perform impedance matching theelectrical signal. For example, the isolation unit may pass theelectrical signal from the second transformers 706 to the inductors 708and the resistors 710. In some embodiments, the inductors 708 and theresistors 710 may operate to provide impedance matching to theelectrical signal. In some embodiments, the inductors 708 and theresistors 710 may operate to perform amplitude attenuation of theelectrical signal. In some embodiments, the inductors 708 and theresistors 710 may operate to limit an amplitude of a current of theelectrical signal. In some embodiments, the inductors 708 and theresistors 710 may operate to perform any combination of the foregoing.

In block 810, the isolation unit may provide a modified electricalsignal. For example, the isolation unit may provide the modified signal754 via the output pins 712. In some embodiments, the output pins 712may be a component of a connector, such as an RJ-45 cable connector, toenable a connection of the isolation unit to a physical connector, suchas the physical connector 110.

The modified signal may propagate along a cable coupled to the isolationunit (e.g., the physical connector 110). In various embodiments, themodified signal (e.g., the modified signal that propagates along thecable) cannot be transformed to extract an intelligible audio signal. Insome embodiments, the unintelligible audio signal may be anunintelligible speech signal.

FIGS. 9A-9H are plots of detected signal amplitude against a test signalfrequency illustrating test results 900 a-900 h of an embodimentisolation unit. The detected signal amplitudes illustrated in FIGS.9A-9H illustrate the performance of an isolation unit operating on aninduced electrical signal to produce a modified signal such that theisolation unit satisfies the Committee on National Security Systems(CNSS) Instruction No. 5001.

With reference to FIGS. 1-9H, the isolation unit (e.g., the isolationunit 102, 400) was tested by exposing the isolation unit to a testsignal that included one or more tones. Measurements were made of amodified signal that was provided by the isolation unit. In the testsrepresented by the test results 900 a-900 h, two output pins (e.g., theoutput pins 712) were selected and an attempt was made to detect amodified signal. The test results 900 a-900 h demonstrate that theembodiment isolation unit under test produced one or more modifiedsignals having a signal level below a threshold signal level (indicatedin FIGS. 9A-9H as “limit”). The threshold signal level illustrated inFIGS. 9A-9H is −120 dB.

The test results 900 a-900 e illustrate that all of the detectedmodified signals are below the threshold signal level. Accordingly, thedetected modified signals in test results 900 a-900 e cannot betransformed to extract an intelligible audio signal.

The test results 900 f-900 h illustrate that most of the detectedmodified signals are below the threshold signal level, and that certainmodified signal levels were detected above the threshold signal level.However, in the test results 900 f-900 h, the modified signal levelsdetected above the threshold signal level are below 400 Hz, and thedetected modified signals illustrated in the test results 900 f-900 halso cannot be transformed to extract and intelligible audio signal.

Various embodiments illustrated and described are provided merely asexamples to illustrate various features of the claims. However, featuresshown and described with respect to any given embodiment are notnecessarily limited to the associated embodiment and may be used orcombined with other embodiments that are shown and described. Further,the claims are not intended to be limited by any one example embodiment.

The foregoing method descriptions and the process flow diagrams areprovided merely as illustrative examples and are not intended to requireor imply that the blocks of various embodiments must be performed in theorder presented. As will be appreciated by one of skill in the art theorder of blocks in the foregoing embodiments may be performed in anyorder. Words such as “thereafter,” “then,” “next,” etc. are not intendedto limit the order of the blocks; these words are simply used to guidethe reader through the description of the methods. Further, anyreference to claim elements in the singular, for example, using thearticles “a,” “an” or “the” is not to be construed as limiting theelement to the singular.

The various illustrative logical blocks, modules, circuits, andalgorithm blocks described in connection with the embodiments disclosedherein may be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and blocks have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the claims.

The hardware used to implement the various illustrative logics, logicalblocks, modules, and circuits described in connection with theembodiments disclosed herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but, in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of communication devices, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. Alternatively, some blocks ormethods may be performed by circuitry that is specific to a givenfunction.

In various embodiments, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored as one or more instructions orcode on a non-transitory computer-readable medium or non-transitoryprocessor-readable medium. The operations of a method or algorithmdisclosed herein may be embodied in a processor-executable softwaremodule, which may reside on a non-transitory computer-readable orprocessor-readable storage medium. Non-transitory computer-readable orprocessor-readable storage media may be any storage media that may beaccessed by a computer or a processor. By way of example but notlimitation, such non-transitory computer-readable or processor-readablemedia may include RAM, ROM, EEPROM, FLASH memory, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that may be used to store desired programcode in the form of instructions or data structures and that may beaccessed by a computer. Disk and disc, as used herein, includes compactdisc (CD), laser disc, optical disc, digital versatile disc (DVD),floppy disk, and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofnon-transitory computer-readable and processor-readable media.Additionally, the operations of a method or algorithm may reside as oneor any combination or set of codes and/or instructions on anon-transitory processor-readable medium and/or computer-readablemedium, which may be incorporated into a computer program product.

The preceding description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the embodiments. Thus, various embodiments are notintended to be limited to the embodiments shown herein but are to beaccorded the widest scope consistent with the following claims and theprinciples and novel features disclosed herein.

1. An isolation unit, comprising: input pins configured to receive aninduced electrical signal that is induced by ambient sound wavesincident on an appliance when the appliance is in a powered-off state;one or more first transformers, connected to at least a portion of theinput pins, configured to electrically isolate the induced electricalsignal; one or more second transformers, connected to the one or morefirst transformers, configured to receive the induced electrical signalfrom the one or more first transformers, and further configured toprovide a common mode choke function on the induced electrical signal;and output pins, connected to the one or more inductors, configured toreceive a modified electrical signal from the one or more inductors, andfurther configured to propagate the modified electrical signal to adownstream cable.
 2. The isolation unit of claim 1, wherein the one ormore first transformers are further configured to provide a frequencyfiltration function on one or more frequencies of the induced electricalsignal.
 3. The isolation unit of claim 1, wherein the one or more secondtransformers are further configured to cancel one or more aspects of anamplitude of the induced electrical signal.
 4. The isolation unit ofclaim 1, wherein the modified electrical signal may not be transformedinto an intelligible audio signal. 5-28. (canceled)
 29. The isolationunit of claim 1, further comprising: one or more inductors connected tothe one or more second transformers and one or more resistors connectedto the one or more inductors, wherein the one or more inductors and theone or more resistors are configured to limit an amplitude of a currentof the induced electrical signal.
 30. The isolation unit of claim 1,wherein the induced electrical signal is one of: triboelectricallyinduced by the ambient sound waves incident on the appliance; orpiezoelectrically induced by the ambient sound waves incident on theappliance.
 31. The isolation unit of claim 1, wherein the one or morefirst transformers are configured to attenuate one or more frequenciesof the induced electrical signal in a range of from approximately 200 Hzto approximately 10,000 Hz.
 32. The isolation unit of claim 1, whereinthe one or more first transformers are configured to attenuate one ormore frequencies of the induced electrical signal in a range of fromapproximately 300 Hz to approximately 5,000 Hz.
 33. The isolation unitof claim 1, wherein the amplitude of current of the modified electricalsignal is substantially below −120 dB.
 34. A method of modifying aninduced electrical signal that is induced by ambient sound wavesincident on an appliance, comprising: receiving, at input pins, theinduced electrical signal when the appliance is in a powered-off state;electrically isolating the induced electrical signal by one or morefirst transformers connected to at least a portion of the input pins;receiving, at one or more second transformers connected to the one ormore first transformers, the induced electrical signal; providing, bythe one or more second transformers, a common mode choke function on theinduced electrical signal; and outputting a modified electrical signalfrom the one or more inductors and propagating the modified electricalsignal to a downstream cable via output pins connected to the one ormore inductors.
 35. The method of claim 34, wherein electricallyisolating the induced electrical signal by one or more firsttransformers connected to at least a portion of the input pinscomprises: providing by the one or more first transformers a frequencyfiltration function on one or more frequencies of the induced electricalsignal.
 36. The method of claim 34, wherein providing a common modechoke function on the induced electrical signal comprises: canceling theone or more second transformers one or more aspects of an amplitude ofthe induced electrical signal.
 37. The method of claim 34, whereinoutputting the modified electrical signal comprises outputting anelectrical signal that may not be transformed into an intelligible audiosignal.
 38. The method of claim 34, further comprising: limiting, by oneor more inductors connected to the one or more second transformers andone or more resistors connected to the one or more inductors, anamplitude of a current of the induced electrical signal.
 39. The methodof claim 34, wherein receiving the induced electrical signal comprisesreceiving an electrical signal that is: triboelectrically induced by theambient sound waves incident on the appliance; or piezoelectricallyinduced by the ambient sound waves incident on the appliance.
 40. Themethod of claim 34, wherein electrically isolating the inducedelectrical signal by one or more first transformers connected to atleast a portion of the input pins comprises: attenuating by the one ormore first transformers one or more frequencies of the inducedelectrical signal in a range of from approximately 200 Hz toapproximately 10,000 Hz.
 41. The method of claim 34, whereinelectrically isolating the induced electrical signal by one or morefirst transformers connected to at least a portion of the input pinscomprises: attenuating by the one or more first transformers one or morefrequencies of the induced electrical signal in a range of fromapproximately 300 Hz to approximately 5,000 Hz.
 42. The method of claim34, wherein outputting the modified electrical signal comprisesoutputting an electrical signal having an amplitude of current that issubstantially below −120 dB.